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Glaciers seed ocean with silicon – and fuel plankton growth

The base of glaciers could be a huge source of silicon

Christophe Boisvieux/Corbis

By Colin Barras

From icy water comes life. The meltwater beneath Greenland’s glaciers is an important source of the silicon that some plankton need to build their glassy skeletons – and climate change could alter the input.

But large plankton blooms might become less likely to form without the ready supply of silicon.

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The base of glaciers is a hotbed of physical and chemical activity as the ice grinds away at the rock below. For instance, we know that the process frees up hundreds of thousands of tonnes of iron that is then carried to the sea in meltwater, fertilising the ocean and allowing plankton to thrive.

Jon Hawkings at the University of Bristol, UK, and his colleagues wondered what else might be transported in the meltwater. Previous work had suggested that the process frees up silicates, so the researchers have begun assessing how much silicon the meltwater dumps into coastal waters.

“It’s early days but our estimates indicate that the ice sheets could be a huge source of silicon to the polar regions,” says Hawkings. Most of this comes from silicon attached to the sediments suspended in the meltwater that on reaching the ocean dissolve into the salt water.

Silicon abundance

Hawkings says the high abundance of diatoms in Greenland’s coastal waters could be a direct result of the meltwater’s silicon influx. He presented the findings at the Goldschmidt conference in Prague, the Czech Republic, last week, and plans to publish figures detailing the quantities of silicon in meltwater in the next few months.

“Although more work needs to be done to properly quantify this, we believe it is highly likely these inputs will change in a warming climate,” says Hawkings.

The idea makes sense, says Matt Charette at the Woods Hole Oceanographic Institution in Massachusetts. “It’s certainly possible that the runoff from the Greenland ice sheet may help recharge the ecosystem during summer when meltwater reaches a maximum,” he says.

But the same process might not be as important around Antarctica, where the waters are naturally rich in silica. There, iron is probably the limiting factor on diatom growth, says Charette.